The invention relates generally to Therapeutic proteins (including, but not limited to, at least one polypeptide, antibody, peptide, or fragment and variant thereof) fused to albumin or fragments or variants of albumin. The invention encompasses polynucleotides encoding therapeutic albumin fusion proteins, therapeutic albumin fusion proteins, compositions, pharmaceutical compositions, formulations and kits. Host cells transformed with the polynucleotides encoding therapeutic albumin fusion proteins are also encompassed by the invention, as are methods of making the albumin fusion proteins of the invention using these polynucleotides, and/or host cells.
Human serum albumin (HSA, or HA), a protein of 585 amino acids in its mature form (as shown in FIG. 1 (SEQ ID NO:1)), is responsible for a significant proportion of the osmotic pressure of serum and also functions as a carrier of endogenous and exogenous ligands. At present, HA for clinical use is produced by extraction from human blood. The production of recombinant HA (rHA) in microorganisms has been disclosed in EP 330 451 and EP 361 991.
Therapeutic proteins in their native state or when recombinantly produced, such as interferons and growth hormones, are typically labile molecules exhibiting short shelf-lives, particularly when formulated in aqueous solutions. The instability in these molecules when formulated for administration dictates that many of the molecules must be lyophilized and refrigerated at all times during storage, thereby rendering the molecules difficult to transport and/or store. Storage problems are particularly acute when pharmaceutical formulations must be stored and dispensed outside of the hospital environment.
Few practical solutions to the storage problems of labile protein molecules have been proposed. Accordingly, there is a need for stabilized, long lasting formulations of proteinaceous therapeutic molecules that are easily dispensed, preferably with a simple formulation requiring minimal post-storage manipulation.
Upon in vivo administration, therapeutic proteins in their native state or when recombinantly produced, such as interferons and growth hormones, exhibit a short plasma stability due to rapid clearance from the bloodstream. Accordingly, the therapeutic effects provided by these proteins are also short-lived. Thus, in order to sustain their desired therapeutic effect in vivo, the rapid clearance of these proteins from the blood dictates that the therapeutic molecules must be administered more frequently or at a higher dose. However, increasing the dosing schedule for administration of the therapeutic protein often results in an increase in injection site reactions, side-effects, and toxicity in the patient. Similarly, administration of the therapeutic protein at a higher dose also commonly results in an increase in toxicity and side-effects in the patient.
The few practical solutions to increasing plasma stability of therapeutic molecules that have been proposed, including chemical conjugation, have provided limited benefit to the patient. Generally, in most cases, these chemically modified therapeutic molecules are still administered on a frequent dosing schedule, retaining significant injection site reactions, side-effects, and toxicity in patients. Accordingly, there is a need for an stabilized form of therapeutic molecules that retains a higher plasma stability in vivo than the native or recombinantly produced therapeutic alone and can be administered less frequently, thereby decreasing potential side-effects to the patient.